The Field Density Test Calculator helps engineers, contractors, and quality inspectors check how well soil has been compacted at a construction site. Good soil compaction is important because it supports the strength and safety of roads, buildings, and embankments. This tool lets users quickly find the bulk density, dry density, moisture content, and degree of compaction without doing manual calculations each time. It belongs to the Soil Testing and Construction Quality Calculator category and is commonly use in civil engineering and geotechnical work.
formula of Field Density Test Calculator
- Bulk Density (Wet Density):
Bulk Density = Weight of Wet Soil / Volume of Hole
Where:
Weight of Wet Soil is the mass of the excavated soil sample (in kg or lb)
Volume of Hole is the space made in the ground (in m³ or ft³)
The volume is usually find by filling the hole with sand.
- Dry Density:
Dry Density = Bulk Density × (1 − w)
or
Dry Density = Weight of Dry Soil / Volume of Hole
Where:
w is the water content written as a decimal (for example, 10% moisture is 0.10)
Weight of Dry Soil is find by drying the wet soil in an oven.
- Moisture Content:
Moisture Content (w) = (Weight of Water) / (Weight of Dry Soil)
Where:
Weight of Water = Weight of Wet Soil − Weight of Dry Soil
- Degree of Compaction (optional):
Degree of Compaction (%) = (Field Dry Density / Maximum Dry Density) × 100
Maximum Dry Density comes from a Proctor test done in a lab.
Units used:
Density is usually shown in kg/m³ or lb/ft³.
Common Field Density Test Reference Table
This table shows typical acceptable compaction levels for various soil types used in construction.
| Soil Type | Typical Maximum Dry Density (kg/m³) | Common Degree of Compaction (%) |
|---|---|---|
| Well-graded Sand | 1,800–2,000 | 95–100 |
| Clayey Soil | 1,600–1,800 | 90–95 |
| Gravelly Soil | 2,000–2,200 | 95–100 |
| Silt | 1,400–1,600 | 90–95 |
This helps compare your field results with standard values.
Example of Field Density Test Calculator
Let’s check an example step by step.
Given:
Weight of Wet Soil = 20 kg
Weight of Dry Soil = 18 kg
Volume of Hole = 0.01 m³
Maximum Dry Density from lab (Proctor test) = 1,900 kg/m³
- Bulk Density:
Bulk Density = 20 / 0.01 = 2,000 kg/m³ - Moisture Content:
Weight of Water = 20 − 18 = 2 kg
Moisture Content = 2 / 18 = 0.111 (or 11.1%) - Dry Density:
Dry Density = 2,000 × (1 − 0.111) = 2,000 × 0.889 = 1,778 kg/m³
Or directly: 18 / 0.01 = 1,800 kg/m³ (slight rounding difference) - Degree of Compaction:
Degree of Compaction = (1,778 / 1,900) × 100 ≈ 93.6%
This means the soil is compacted to about 93.6% of the lab maximum.
Most Common FAQs
Field density testing checks if soil is compacted enough to handle loads from buildings, roads, or other structures. Poor compaction can cause settlement or failure later.
It depends on project size and soil conditions. Many projects test every layer or every fixed area to make sure all parts meet standards.
If compaction is low, the area should be re-compacted or adjusted until it meets the target value. This prevents future problems like cracks or sinking.